Contouring tracer



Mayl. 1 928.

J. c. SHAW ET AL CONTC'URING TRACER Original Filed Oct. 28, 1924 4Sheets-Sheet 1 I N V EN TOR I MAL/0w. 44w- ATTORNEYX.

' J. C. SHAW ET AL CONTOURING TRACER Original Filed Oct. 28. 1924 4Sheets-Sheet 2 .u/ wyww M INVENTO f i ATTORNEW May 1,1928.

J. c. SHAW ET AL CONTOURING TRACER Original Filed Oct. 28. 1924 y n b mN. hm um. may I \mk.

J z\ m E Q E mm v a R \mu m N? m 2% E NK J. C. SHAW ET AL May I, 192%;

CONTOURING TRACER 4 Sheets-Sheet 4- Original Filed Oct. 28. 1924 V BYATTORNEYS.

Patented May 1, 1928.

UNITED STATES PATENT OFFICE.

1 JOHN C. SHAW AND ROBERT D. SHAW, OF BROOKLYN, NEW YORK, .ASEIGNORS TO2 KELLER MECHANICAL ENGINEERING CORPORATION, OF BROOKLYN, NEW YORK, A

CORPORATION OF NEW YORK.

CONTOURING- TRACER.

Application filed October 28, 1924, Serial No. 7465548. Renewed October17, 1927.

Our invention relates more particularly to the electro-magnetic controlof machine tools, in which feeds are provided for feeding the work intwo rectilinear directions at right angles to each other in the sameplane, and a contouring tracer is adapted to follow a model, pattern ortemplate and so control the two feed motions, as to reproduce thepattern by the action of a suitable cutter upon the work.

In the pending application of John C. Shaw, Serial No. 687,758, filedJanuary 22, 1924:, there is shown and described a contouring tracer forcontrolling the feeds in two rectilinear directions, as above indicated,said contouring tracer being provided with electro-magnet interlocks forbreaking the circuits under predetermined conditions. It is founddesirable to simplify the construction and make the device as sensitiveas possible, therefore, in the present improvement, it is contemplatedto substitute for the electrical interlock of the above application, amechanically operated interlock for controlling the circuits for thefeeds in the two rectilinear directions.

In carrying out this object, the arrangement of the circuit closingcontacts is much simplified and instead of the relay contacts for directand reverse feed being carried upon -movable levers actuated by thetracer, the direct feed contact points in the present improvement, arefixed and cooperate directly with the button end of the tracer spindlethrough which the circuits are grounded. In the present improvement, thereverse feed contact points are carried upon pivoted levers and solocated as to cooperate with the button on the end of the tracer spindlefor closing the circuits therethrough, but it will be understood that,as in the pending application referred to, the reverse feed contacts arenormally opened, while the direct feed contacts are normally closed. f I

It is desirable at times, under certain operatin conditions, for thedirect feed contact circuits to be broken or opened when the reversefeed contact circuits are closed, and this is accomplishedelectro-magnetically in the device of the prior application, abovereferred to, but in the present improvement, the direct feed contactcircuits are broken by a; slight movement of the respective leverscarrying the reverse feed contacts, such movement being effected bymovement of the tracer spindle. Such movement of the tracer spindlemoves the contact button on the end of the spindle out of engagementwith one of the direct feed contacts .and into engagement with a reversefeed contact, the movement of the lever of which is arranged to breakthe circuit of the other direct feed contact, thus providing a purelymechanically operating interlock.

One form of our improved contouring tracer and mechanical interlock isshown in the accompanyingdrawings, in which Fig. 1 shows a frontelevation of our improved contouring tracer; Fig. 2 is a sectionaldetail of one of the circuit closing contacts of the interlock; Fig. 3is a transverse longitudinal section of the contouring tracer, as shownin Fig. 1, except that, for the purpose of illustrating the balancingdevice for the tracer gram of the relays and magnetic clutch feeddevices, and Figs. 6 to 14 are diagrams for illustrating the operationof the device.

Referring to the drawings, the tracer body comprises a head 1 in which atubular body portion 2 is secured, and through the center of both thehead and tubular portion a tracer or spindle 3 extends. The outer end ofthe tubular portion 2 is counterbored and fitted with a ball socketbearing ring 4, which is held in place by a thimble 5, screw threadedinto the end of the tube 2, (Fig. 3). The body of the tracer spindle 3is provided with a sphericalsegment 6 in the form of a collar secured inplace by a suitable nut 7, so as to form a universal bearing with theball socket 4, for the tracer spindle. The walls of the thimble 5 may bethick enough tooverhang the collar 6 to prevent withdrawal of the tracerspindle from the tubular body portion 2. The outer end of the tracerspindle 3 extends beyond the end of the body portion 2 and carries atracer head 8, which may be preferably secured thereto by a nut 9, sothat the head 8 may be removably ating for the interchange oftracerpoints or heads of different sizes. The inner end of the tracerspindle extends throu h the head 1 and terminates in a buttonll a aptedto engage contact points for closing relay circuits by grounding throughthe tracer spin- ,dle, as hereinafter explained.

Since the size of the tracer head 8 may be varied it will be understoodthat the balance of thetracer spindle, asa whole, may vary and, for thisreason, it is preferable to provide means for accurately balancing thespindle when in use. For this purpose, a tubular plug 12 is preferablyinserted on the underside of the forward end of the tubular body portion2, as shown in Fig. 3 of the drawings, and this plug contains a movablesolid plug or feeler 13, engaging the underside of the end 10'of thetracer spindle. A spring 14 is inserted between the lower end of theplug 13 and a screw 15 threaded into the lower end of the tubular plug12. It will thus be seen that by adjusting the screw 15, the pressure ofthe spring 14 can be regulated to properly balance the tracer spindle310 and a lock nut 16 will hold the screw in proper adjustment.

As more particularly shown in Figs. 1 and 3 of the drawings, it will beseen that the head 1 of the tracer body is preferably made up of arecessed casting, the forward end of which is bored out at 17 to receivea rotatable contact carrying block 18. The block 18 may be of anysuitable insulating material and is preferably annular in form andmounted upon a tubular hub 19, which is rotatably mounted in a bearingformed in an inwardly projecting flange 20 of thcIhead 1., A bearing andspacing collar 21 is preferably mounted on the tubular hub 19 and may beutilized to hold the contact carrying block 18 in place, while itsopposite face forms a bearing against the" face of the counter bore 17and flange 20. Theother face of the flange 20 serves as a thrust hearingfor an annular bevel gear 22, which is secured to the end of thehub 19by suitable screws 23.

Referring to Fig. 3, it will be seen that the annular bevel gear 22 isengaged'by a bevel pinion 24, secured to the end of a shaft 25 extendingthrough a tube 26 projecting from the side of the head 1. The tube 26 isheld in place in the head 1 by a suitable screw as at 27 and the outerend of the tube is provided with a housing 28, secured thereto by ascrew 29. The shaft 25 extends into the housing 28 and the inner endthereof is provided with a bevel pinion 30, engaging a bevel gear 31,which is secured to a short shaft 32 rotatably mounted transversely inthe housing 28, as indicated in Fig. 3. The front wall of the housing 28is preferably circular 'in form and provided; with four index studs 33,while a pointer 34, secured to the shaft 32, is adapted to cooperatetherewith. A handle 35 is preferably cast integral with the pointer 34,the handle not only serving to adjust the pointer, :but serving as anindex in itself, for it is spaced from the pointer 34, and its relationto the index studs 33 is of importance as will be more fully explainedhereinafter.

It will be seen that by rotating the shaft 32 by means of the handle 35,the contact carrying block 18 may be rotated with re spect to the tracerhead 1. The contact carrying block 18 is preferably provided with fourcommutator segments 36, which are located in the respective quadrantsthereof, as

more particularly indicated in the diagram in Fig. 5 of the drawings.The segments 36 are insulated from each other and spaced apart at theirends and. may be referred to as ABC and D. The segments A and B are soconnected up, through suitable contacts and contact circuits as tocontrol respectively, through suitable relays, the direct and reversefeed in one-rectilinear direction and the segments 0 and D are similarlyconnected up to control the other feed in the same manner, so that inany position of rotation of the contact carrying block 18, the relationbetween the various segments will not be changed, but the pairs ofsegments A, B, C and D may be brought into position to control thedirect and reverse feed of the machine in two rectilinear directions, aspreviously referred to, at each of the four index points or quadrants ofrotation of the block 18 or pointer 34.

In our improved construction, two of the quadrant segments 36,designated as A and D, are v provided with inwardly extending lugs orarms 37 and 38 embedded in the incontact carrying screws 43 and 44,carrying contacts 45 and 46 located 90 apart and adapted to lie inposition to cooperate with and be engaged by the contact button 11 onthe end of the tracer spindle. The contacts 45 and 46 are normallyslightly spaced away from the contact button 11, so that the circuitstherethrough are open and it will be noted that the respective contactcarrying screws 43 and 44 are adjustably mounted in The studs 39 areadapt- 'ed position. The outer ends of the levers 40 and 41 are providedwith circuit closing contacts 48, supported upon bolts 49, passingthrough insulating thimbles (see Fig. 2) in holes in the respective.ends of the levers 40 and 41, the bolts 49 being secured in positionby, suitable nuts 51.-

Each of the quadrant segments 36, desig-' nated as B and C, is'providedwith an inwardly projecting lug 52, which has a boss 53 projecting tothe front surface of the insulating material of the head 18 and bysuitable screws 54, short lead wires 55 and 56 are connected therewith,the opposite ends of the lead wires 55 and 56 bein secured respectivelyto the ends of the L carrying the contacts 48 of the levers 40 and 41,substantially as shown in Figs. 1 and 5 of the'drawings. The circuitclosing contacts 48 cooperate with contacts 57 mounted respectively uponfixed supporting posts 58 and 59, embedded in the insulating materiaL ofthe head 18 and projecting above the front face-thereof, the posts beingarranged 90 apart. Each post 58-59 is provided with a radially extendingcontact carrying screw 60 and 61, adjustably mounted in the respectiveposts, and adapted to be secured in adjusted position by suitable nuts62. The respective screws 60 and 61 are provided with contact points 63and 64, located in position to engage the contact button 11, on the endof the tracer spindle; these contact points being arranged 90 apart,and'diametrically opposite the movable contact points 45 and 46, as willbe seen in Figs. 1 and 5 of the drawings. The

relatively fixed contact points 63 and 64 are adapted to control directfeeds of the machine in tWo rectilinear directions at right angles toeach other and normally the contacts are closed so as to ground thecircults through the contact button 11 and tracer 3. To hold the contactbutton 11 normally in engagement with the fixed contact points 63 and64' a-suitable spring or resil-. lent member 65 (see Fig. 1) is mountedradially, mid-way between the two fixed contact screws, and is effectiveto close both contacts 63 and 64.

It will thus be seen that the fixed contact points 63 and 64, normallyengaging the'contact button 11, are electrically connected through thecontacts 57 and 48 and lead wires 55 and 56, with two of the segments 36designated respectively as C and B. On

the other hand, the movable contacts 45 layswhich are brought intoaction only by.

movement of the tracer button 11, while the tracer is following apattern. It will be observed that the levers 40 and 41 are under springtension, by means of aspring 66, which draws the levers toward eachother,

and thereby holds the circuit contacts 48-" 57 normally closed, so thatcontrol points 63 and 64 close circuits through segments C and B, tooperate relays, controlling direct feed in the two rectilineardirections. The spring 66 isconnected through a block or link 66*, ofinsulating mate rial, thus insulating the levers.

Arranged around the flange 67 of the head 1 of the machine, in therespective quadrants thereof are brushes 68 adapted to cooperate withthe commutator segments 36. The brushes 68 are preferably carboncylinders, and springs 69 (see Fig. 1), adjustably held in place byscrew caps 70, are adapted to hold the brushes in contact with thecommutator segments 36 on the periphery of the contact-carrying block18. The tubes 68 holding the brushes 68, are insulated from the tracerhead flange 67 and, by suitable binding nuts, each is connected to arelay controlling one direction of feed movement of the machine, and,preferably, the various circuits may be connected up as shown in Fig. 5of the drawings,-the letters NS WE, representing. the points of thecompass, are preferably used and referred to in describing the operationof the machine; north meaning up feed; south, down feed; east, feed totheright, and west, feed to the left.

Referring to the wiring diagram, as shown in Fig. 5 of the drawings, itwill be seen that the brush 68, marked N, isconnected by a wire 71, withthe magnets 72 (marked N) of a relay, the circuit being completedthrough lead wires 73 and 74 to the low voltage generator 75. The latteris also connected to ground, so that the circuit is completed throughthe machine, for, as

previously pointed out, the several contacts ,or upward feed ofthemachine. The 110 volt circuit, passing'through the armature 78, passesthrough wire 81"from the main lead,:'8 2 and the circuit from themagnetic clutch; (N) 80 is completed through wire 83 to the main returnlead 84.. Similarly, if the armature 7 8 is actuated by the magnet (S)77, connected with the, brush 68 marked S, the 110 volt circuit will beconnected through wire 85 with the magnetic clutch 86 (marked S)controlling the downward feed movement.

' In like manner,'the brushes 68, hearing the letters VI and E, areconnected respectively to relay magnets 87 (marked W) and 88 (marked E)by wires 89 and 90. The relay magnets (E) 88 and (W) 87 cooperate withthe single armature 91, which, like the armature 78, is adapted to movein one direction or the other, according to which magnet is energized,to close the 110 volt circuit through wires 92 or 93 to actuate one orthe other of the magnetic clutches 94 (marked E) and 95 (marked W), andcontrolling respectively, the feed of the machine to the right or to theleft. The circuits from the respective clutches 80--869495 are completedthrough the wires 83 to the lead 84, as indicated in Fig. 5 of thedrawings.

As represented in Fig. 5, it will be understood that normally, when thetracer is out of contact with the model or pattern, the button 11, underthe influence of the spring 65 will close the contacts 63 and 64, thereby completing circuits through brushes 68, marked N and E In otherwords, the two feed magnetic clutches marked N and E (80 and 94) will beactuated and the direct feeds will be up and to the right. If the rateof feed is the same in both directions, the resultant directionof motionwill be at an angle of or northeast. If thetracer engages the wall ofthe pattern, when the direct feed movement is in the resultant directionor 45, one or the other of the contacts-63 or 64 will be broken and theother rectilinear motion will continue. For instance, as shown in Fig. 5of the drawings, if the up feed or north magnetic clutch is deenergized,so that this motion will stop, the magnetic clutch marked E willcontinue to feed toward the right or east so long as the contact 64remains in engagement with the contact button 11. l

The space between the contact points 63 and 46, and 64 and 45, onopposite sides of the contact button 11, is such that in normaloperation, one of the feed contacts 63 or 64 may be broken to stop thedirect feed without the button engaging the diametrically .oppositemovable contact4546, but it, through some irregularity in the contouringsurface being traced, the tracer is moved excessively, the opposite orreverse feed contact 45 or 46 will be closed by grounding through thebutton and the pressure exerted against the movable contact throws thecorresponding lever outward and breaks the circuit through thecorresponding contacts 4857, connected withthe other direct feed fixedcontact point,

i eee eie" tion with electro-magnetic clutches controlling the feeds intworectilinear directions,

substantially as shown and described in Pat ent No. 1,506,454, of August26, 1924, to John C. Shaw.

It will be understood that the great value and importance of ourimproved interlock contouring tracer lies in the utility of the devicefor operating upon models or templates of extremely complicated contour,as well as upon those of simple contour. In order to illustrate theoperation in connection with a more or less complex 'job, attention iscalled to the diagram of Fig. 4 of the drawings where the stepsofmovement of the contouring tracer are shown enlarged or magnified manytimes. This illustration of the operation is more particularly adaptedto sho-wthe action of the interlocking mechanism and how the tracer willfollow a humpy or irregular job, without rotating the contact carryingblock 18 and the associated contact points to the extent that ordinarilyshould be done, as explained later. In other words, this will explainhow the tracer will work itself over a small hump contour of the patternat (2) the west feed will stop and the west contact will be open, butthe north feed will continue and contact button 11, after breaking thewest feed,

will be thrown'over far enough to close the back feed contact 46 for thereverse or east feed and'the tracer will be moved to (3). When the relaycircuit through the back contact 46 and the relay88iE is operating, itwill be understood that the mechanical interlock will be brought intoaction by the thrust of the button 11, which moving the lever 41, willpositively break the contacts 48-57 in the north feed circuit.

Ill

As soon as the tracer moves east to the point 3) the east or reversecontact 46 will be bro en and the north feed circuit will be closed byclosing the contacts 48-57. The tracer will then move to position (4).Here the operation will be again repeated,

that is, closing the east contact and breakfollowing up the curve to thepoint (6).

Here it will be seen that the north movement against the curve of themodel ceases to give pressure enough to open the east contact but; thecontact controlling the west feed through the relay 87W/" will remainbroken and thefeed will be north or up to the point. (7). As soon,however, as the tracer moves away from the contour far enough to permitcontact 63 to close through the button 11, the west relay 87W will againthrow the magnetic clutch for the west feed and the movement will benorthwest to the point (8) Here again the west feed will be broken andthe feed will be northand this will be repeated indefinitely untiltracer arrives at the point (A), at which point, it will be seen thatthe northwest direction is tangent' to the curve and the tracer willpass oh the contour. It is then necessary to rotate the pointer 34counterclockwise to a corresponding position relative to the next indexpost 33, SW.

The preferred operation, particularly for a simple model or template,having an. external contour to be reproduced, may be illustrated inconnection with the diagrams shown in- Figs. 6 to 13. Assuming the modelto have straight horizontal sides and a rounded end, it will be seenthat if the machine is started, as shown in Fig. 6, with the pointer.34on the index 33, designated as NE, the direction of feed will benortheast, as indicated by the arrow crossing the circle just below themodel. As soon as the tracer strikes the periphery of the model, thenorth. or up feed will be stopped by breaking the direct feed contact63, while the feed toward the east (right), controlled through thecontact 64 and relay 88 (E) will continue until the tracer reaches thepoint (A) where the curve begins. Then, as shown in Fig. 7, both thenorth and east contacts will operate intermittently to carry the traceraround the curve and, preferably, the pointer 34 is moved to theposition indicated in Fig. 7 and maintained practically parallel to atangent to the curve at the point of contact of the tracer. Obviously,this does not change the two directions of feed, but facilitates theaction of the tracer spindle or button 11 on the feed-contacts 63 and 64by maintaining the resultant direction of feed, at all timessubstantially at 45 to the contact screws and 61, thus equalizing theelfect of any movement of the tracer.

The north and east feed motions should be continued until the tracer (A)reaches the point indicated in Fig. 8 of the drawmgs. past the NE indexto the position indicated in Fig. 8. This brings into action the northand west feed control relays. This movement of the handle 35 past theindex NE, it will be understood, is necessary, for as shown in Fig.5,the commutator segments 36 are spaced apart and the relation between thehandle 35 and the segments is such that, when the handle 35 .isimmediately over one ,of the index points 33, the brushes 68 are on theinsulating material of the contact carrying block 18, between thesegments 36, therefore, these points, being dead points, both feeds willbe cut out. If the handle 35 is not, moved from the position of Fig. 7to a position beyond the index point, as shown in Fig. 8, the tracerwould continue in the northeast direction, as indicated by the tangentline and arrow in Fig. 9 of the drawin s.

After the handle 35 has been moved to the position shown in Fig. 8, thenorth and west feeds will.be in operation simultaneously or alternately,while following the curve up to the point (A) in Fig. 10 of thedrawings, and here again, if the handle 35 and pointer are not moved,beyond the dead point, the tracer would continue in a line tangent tothe curve in the northwest direction. The handle 35 should, therefore,be moved to the position shown in Fig. 11, after which the two feeds inoperative control will be south and west. These will continue to finishthe curve to the point (A). in Fig. 11 and, after Then the handle 35should be moved the curve merges into the straight line at the byopening the east contact. When the tracer reaches the lower left handcorner of the model, as indicated in Fig. 13 of the drawings, the handle35 again should be moved, so as to bring the pointer 34 to the NE index,after which the feed will be cast with the north feed suppressed by thenorth A contact being the tracer back to the starting point, asindicated in Fig. 6 of the drawings.

When the model or pattern to be reproduced has an internal contour, theopera tions are substantially the same asthose deheld open. This willbring scribed for Figs. 6 to 13, except that, as shown in Fig. 1a, thetracer (A) is on the inside of the pattern and, of course, can never runoff or out of contact with the contour of the pattern. Furthermore, whenworking on an internal contour, as illustrated in Fig. 14, it ispreferable to work around the contour in clockwise direction, while, aspreviously described, when operating on an external contour, as shown inFigs. 6 to 13;, it is preferred to work around the model and index dialcounter-clockwise. Therefore, the direction of feed on the lowerinternal edge oftlie model, as shown by the arrow in Fig. 14, will betoward the left, provided the handle 35 is turned as it should be, sothat the pointer is at the SW' index 33. in this position the south feedwill be suppressed, while the west feed will continue until the tracerreaches the corner, when it will be stopped by the breaking of thecontact. The pointer 34: should then be turned to the index NW, afterwhich the north feed will carry the tracer to the upper left corner, lhepointer should then be turned to the index NE and the operationcontinued until the curve is reached, after which the tracer is workedaround the curve, substantially as previously described.

lit will be understood that the rate of feed in the two rectilineardirections should be the same for the best results, and it is found inpractice that a feed of two (2) inches per minute gives satisfactoryresults and, preferably the feed should not exceed 2% inches per minute.It will also be understood that, when following a curve, the circuitsare interrupted by breaking the con tacts momentarily, so that, whilethe feed, as represented in magnified form in Fig. 4: of the drawings,produces a saw-tooth edge, the interuptions are so rapid and the amountof feed prior to the interruptions is so small, that the teeth formedare really microscopic, therefore, the result is a substantiallyaccurate reproduction of the curve of the contour.

While we have shown ourimproved contouring tracer in the preferred form,it will be understood that we do not wish to be limited in theinterpretation of the claims, to the specific details shown, for variousmodifications may be made therein without departing from the spirit andscope of the invention.

We claim 1. A contouring tracer comprising a tracer spindle providedwith a contact button at one end, a pair of contact points, maintained 7in fixed position relative to said button, said contact points being 90apart, and adapted to be connected withsuitable'relays for controllingdirect feed in two directions at right angles to each other, the circuitbeing completed by grounding through said button a central openingthrough which the end of said spindle passes, a pair of contacts mountedon said head 90 apart, and adapted to be engaged by said button forgrounding the respective circuits of said contacts through said tracerspindle, resilient means for normally holding the button inengagementwith said contacts, and 'manual means for rotating said head.

3. A contouring tracer comprising a movable tracer spindle provided witha contact button at one end, a head concentrically arranged for rotationabout the button end of said spindle, a pair of contact points 90 apart,mounted upon said head, commutator segments mounted upon said head andelectrically connected with said contact points and means actuated bymovement of said tracer spindle for breaking the circuits between saidcontact points and the respective segments.

4. The contouring tracer as claimed in claim 3, in which four brushesare provided at diametrically opposite points for engagement with saidcommutator segments and means is provided for rotating said head so asto vary the engagement of the segments and brushes.

5. A contouring tracer comprising a movable tracer spindle provided witha contact button at one end, a rotatable head mounted concentrically ofthe button end of said spindle, a pair of contacts 90 apart, mounted onsaid head for engagement with said button, four commutator segmentsmounted on said head in the respective quadrants thereof, electricalconnections between said contacts and two ofsaid quadrants lyingadjacent, resilient means for holding the button nor mally in engagementwith said contacts, a

second pair of contacts electrically connected respectively with theother two of said segments, said second contacts being adapted to beengaged by said contact button when said spindle is moved apredetermined amount, and means controlled by said button when engagingsaid last mentioned contacts for breaking the circuits between saidfirst mentioned contacts and their respective segments.

6. A contouring tracer, comprising a tracer spindle mounted foruniversal movement of its ends and provided at one end with a contactbutton, a head provided with an opening through which the button end ofsaid spindle extends, a pair of fixed contact points mounted on saidhead 90 apart in position to cooperate with said contact and resilientmeans for holding said button in engagement with said fixed contactpoints 7. The contouring tracer as claimed in claim 6, in which saidhead is mounted for rotation about. said spindle and manual means isprovidedfor rotating it.

8. The contouring tracer as claimed in 7 claim 6, in which said head is-mountedfor rotation about said spindle, and is provided with fourcommutator segments electrically connected respectively to the fixed andlever contact points to complete circuits by grounding through saidbutton and four brushes are mounted 90 apart around said head forcooperation with said commutator segments.

9. A contouring tracer comprising amovable tracer spindle providedwith'a contact button at one end, a head provided with an openingthrough which the button end of said spindle passes, two fixedandtwomovable contact points mounted on said head 90 apart in positionto be engaged by saidcontact button for grounding circuits through saidspindle, and a'spring for normally holding said contact button inengagement with said fixed contact points.

10. The contouring tracer as claimed in claim 9, in which said twomovable contact points, are carried by levers mounted on said head andextending transversely of the axis of said spindle, said movable contactpoints being located in position to be engaged by said button"diametrically opposite the fixed contact points, said lever contactpoints being so a justed as to be normally out of engagement with saidbutton.

11. Thecontouring tracer as claimed in claim 9, in which said movablecontact points are located diametrically opposite said fixed contactpoints, withrespect to said contact button, and means is provided forbreaking the respectivecircuits through said fixed contact points bymovement of-said.

movable contact points.

12.. A contouring tracer comprising a movable tracer spindle providedwith a contact button at one end, a head rotatable con centrically ofthe button end of said spindle, manual means for rotating said head, apair of fixed contact points mounted on said head 90 apart in positionto be engaged by said button, a spring normally holding said button inengagement with said fixedcontact,

points, a pair of movable contact points supported on said head 90 apartand dia-' metrically opposite the respective fixed contacts, fourcommutator segments mounted in the'four quadrants of said rotatable headand each electrically connected respectively 1 to one of said contactpoints, four brushes mounted 90 apart around said head for cooperationwith said commutator segments for completing relay circuits through saidcontacts when the latter are grounded through said contact button, andmeans controlled by the movement of said movable contact points forbreaking the circuits of said fixed contact points.

13. The contouring tracer as claimed in claim 12, in which said movablecontact points are mounted on levers pivoted on said ead and said leverscarry circuit closing contacts normally closing the circuits between thetwo fixed contact points, and their respective segments, springsbeingprovided for holding said levers with said circuit closing contactsclosed. 7

14. A contouring tracer comprising a movable tracer spindle providedwith a contact button at one end, adapted for cooperation with two fixedand two movable contacts, a head concentrically arranged for rotation.about the button end of said spindle, a pair of fixed contact points 90apart, mounted upon said head, four commutator segments mounted uponsaid head two of which are electrically connected with said fixedcontact points through normally closed circuit closing contacts, a pairof movable contacts on said head and permanently in electricalconnection with the other twosegments respectively, and mechanical meansfor breaking said circuit closing contacts when said movable contactsare closed through said contact button.

JOHN G. SHAW.

ROBERT D. SHAW.

